I'm currently trying to book a one way reward flight from Tokyo to London. There is availability on the BA site, and on the flight selection page, the price is listed as 30000 Avios + £18.78 "taxes, fees and carrier charges".

However, when I click continue, the taxes, fees and charges shoot up to £169.90.

Is this a known issue? I was under the (perhaps false) impression that fees out of London were generally high, but not necessarily on the inbound leg.

Many thanks in advance for your help!